Background Service.

Background Service in android is a service which performs an operation that isn't directly noticed by the user.

Examples :

• Downloading a file in background from a server.
• Playing songs in background in a music player app.
• Displaying the status of Connection to the server for a chat messaging app.

Implementation of Background Service.

• Build a new Android project .

• Open up activity_main.xml.

• Now , we're going to add 2 buttons , which is startService and stopService .

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.codingblocks_projects.stoned_coder.ForegroundServices.MainActivity">

    <Button android:id="@+id/btnStartService"
        android:layout_width="0dp"
        android:layout_weight="1"
        android:layout_height="wrap_content"
        android:text="Start Service" />

    <Button android:id="@+id/btnStopService"
        android:layout_width="0dp"
        android:layout_weight="1"
        android:layout_height="wrap_content"
        android:text="Start Service" />
</LinearLayout>

• create a customview.xml in which we're going to create some custom views for our notification panel .

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/notification"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center"
    android:orientation="horizontal">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_toLeftOf="@+id/llPlayControls"
        android:orientation="vertical"
        android:padding="10dp">

        <TextView
            android:id="@+id/notification_text_title"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:ellipsize="end"
            android:lines="1"
            android:singleLine="true"
            android:text="Song Title"
            android:textColor="#787878"
            android:textStyle="bold" />

        <TextView
            android:id="@+id/notification_text_artist"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:ellipsize="end"
            android:lines="1"
            android:singleLine="true"
            android:text="artist"
            android:textColor="#787878" />

    </LinearLayout>

    <LinearLayout
        android:id="@+id/llPlayControls"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_centerVertical="true"
        android:orientation="horizontal">

        <ImageView
            android:id="@+id/notification_button_prev"
            android:layout_width="48dp"
            android:layout_height="48dp"
            android:src="@android:drawable/ic_media_previous" />

        <ImageView
            android:id="@+id/notification_button_play"
            android:layout_width="48dp"
            android:layout_height="48dp"
            android:src="@android:drawable/ic_media_play" />

        <ImageView
            android:id="@+id/notification_button_skip"
            android:layout_width="48dp"
            android:layout_height="48dp"
            android:src="@android:drawable/ic_media_next" />

        <ImageView
            android:id="@+id/notification_button_close"
            android:layout_width="48dp"
            android:layout_height="48dp"
            android:src="@android:drawable/ic_menu_close_clear_cancel" />
    </LinearLayout>


</RelativeLayout>```

* Now in the ```MainActivity.java``` file inside ``onCreate`` , we'll be geting refrence fo the buttons and defining 2 intents , one for start and the other being stop .

 ```java
   startButton=(Button)findViewById(R.id.btnStartService);
 stopButton =(Button)findViewById(R.id.btnStopService);

    startButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent startIntent = new Intent(MainActivity.this, ForegroundService.class);
                startIntent.setAction(Constants.ACTION.STARTFOREGROUND_ACTION);
                startService(startIntent);
            }
        });

    stopButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent stopIntent = new Intent(MainActivity.this, ForegroundService.class);
                stopIntent.setAction(Constants.ACTION.STOPFOREGROUND_ACTION);
                startService(stopIntent);
            }
        });

We'll create a new class and name that as Constants.java

• This class will contain 2 interfaces one for Actions and other for ServiceID

public class Constants {

   public interface ACTION {
       public static String MAIN_ACTION = "com.stonedcoder.alertdialog.action.main";
       public static String STARTFOREGROUND_ACTION = "com.stonedcoder.alertdialog.action.startforeground";
       public static String STOPFOREGROUND_ACTION = "com.stonedcoder.alertdialog.action.stopforeground";
   }

   public interface NOTIFICATION_ID {
       public static int FOREGROUND_SERVICE = 101;
   }
}

• Now we'll create another class and name that ForegroundService which holds the logic for custom notification views and service .

class ForegroundService extends Service {
    private static final String LOG_TAG = "ForegroundService";

    @Override
    public void onCreate() {
        super.onCreate();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        if (intent.getAction().equals(Constants.ACTION.STARTFOREGROUND_ACTION)) {
            Toast.makeText(this,"Start Service",Toast.LENGTH_SHORT).show();
            Log.i(LOG_TAG, "Received Start Foreground Intent ");


            Intent notificationIntent = new Intent(this, MainActivity.class);
            notificationIntent.setAction(Constants.ACTION.MAIN_ACTION);
            notificationIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK
                    | Intent.FLAG_ACTIVITY_CLEAR_TASK);
            PendingIntent pendingIntent = PendingIntent.getActivity(this, 0,
                    notificationIntent, 0);

            RemoteViews notificationView = new RemoteViews(this.getPackageName(),R.layout.customviews);

            // And now, building and attaching the Play button.
            Intent buttonPlayIntent = new Intent(this, NotificationPlayButtonHandler.class);
            buttonPlayIntent.putExtra("action", "togglePause");

            PendingIntent buttonPlayPendingIntent = pendingIntent.getBroadcast(this, 0, buttonPlayIntent, 0);
            notificationView.setOnClickPendingIntent(R.id.notification_button_play, buttonPlayPendingIntent);

            // And now, building and attaching the Skip button.
            Intent buttonSkipIntent = new Intent(this, NotificationSkipButtonHandler.class);
            buttonSkipIntent.putExtra("action", "skip");

            PendingIntent buttonSkipPendingIntent = pendingIntent.getBroadcast(this, 0, buttonSkipIntent, 0);
            notificationView.setOnClickPendingIntent(R.id.notification_button_skip, buttonSkipPendingIntent);

            // And now, building and attaching the Skip button.
            Intent buttonPrevIntent = new Intent(this, NotificationPrevButtonHandler.class);
            buttonPrevIntent.putExtra("action", "prev");

            PendingIntent buttonPrevPendingIntent = pendingIntent.getBroadcast(this, 0, buttonPrevIntent, 0);
            notificationView.setOnClickPendingIntent(R.id.notification_button_prev, buttonPrevPendingIntent);

            // And now, building and attaching the Close button.
            Intent buttonCloseIntent = new Intent(this, NotificationCloseButtonHandler.class);
            buttonCloseIntent.putExtra("action", "close");

            PendingIntent buttonClosePendingIntent = pendingIntent.getBroadcast(this, 0, buttonCloseIntent, 0);
            notificationView.setOnClickPendingIntent(R.id.notification_button_close, buttonClosePendingIntent);



            Bitmap icon = BitmapFactory.decodeResource(getResources(),
                    R.mipmap.ic_launcher);

            Notification notification = new NotificationCompat.Builder(this)
                    .setContentTitle("nkDroid Music Player")
                    .setTicker("nkDroid Music Player")
                    .setContentText("nkDroid Music")
                    .setSmallIcon(R.mipmap.ic_launcher)
                    .setLargeIcon(
                            Bitmap.createScaledBitmap(icon, 128, 128, false))
                    .setContent(notificationView)
                    .setOngoing(true).build();



            startForeground(Constants.NOTIFICATION_ID.FOREGROUND_SERVICE,
                    notification);
        }


        else if (intent.getAction().equals(Constants.ACTION.STOPFOREGROUND_ACTION)) {
            Toast.makeText(this,"Stop Service",Toast.LENGTH_SHORT).show();
            Log.i(LOG_TAG, "Received Stop Foreground Intent");
            stopForeground(true);
            stopSelf();
        }
        return START_STICKY;
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.i(LOG_TAG, "In onDestroy");
    }

    @Override
    public IBinder onBind(Intent intent) {
        // Used only in case of bound services.
        return null;
    }


    /**
     * Called when user clicks the "play/pause" button on the on-going system Notification.
     */
    public static class NotificationPlayButtonHandler extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {
            Toast.makeText(context,"Play Clicked",Toast.LENGTH_SHORT).show();

        }
    }

    /**
     * Called when user clicks the "skip" button on the on-going system Notification.
     */
    public static class NotificationSkipButtonHandler extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {
            Toast.makeText(context,"Next Clicked",Toast.LENGTH_SHORT).show();
        }
    }

    /**
     * Called when user clicks the "previous" button on the on-going system Notification.
     */
    public static class NotificationPrevButtonHandler extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {
            Toast.makeText(context,"Previous Clicked",Toast.LENGTH_SHORT).show();
        }
    }

    /**
     * Called when user clicks the "close" button on the on-going system Notification.
     */
    public static class NotificationCloseButtonHandler extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {
            Toast.makeText(context,"Close Clicked",Toast.LENGTH_SHORT).show();

        }
    }

}

• Now open up AndroidManifest.xml and add recivers and service to the manifest .

<receiver android:name=".ForegroundService$NotificationCloseButtonHandler" />
        <receiver android:name=".ForegroundService$NotificationPlayButtonHandler" />
        <receiver android:name=".ForegroundService$NotificationPrevButtonHandler" />
        <receiver android:name=".ForegroundService$NotificationSkipButtonHandler" />

        <service android:name=".ForegroundService" />````